The present invention relates to improvements in and relating to an apparatus for controlling an electromagnetic valve which is adapted for use in controlling for example, the injection of fuel in an internal combustion engine.
In an electronically-controlled fuel injection system, an electromagnetic valve is provided on an engine for supplying fuel in response to a pulse signal. The electromagnetic valve includes therein an electromagnetic coil and a valve member arranged in such a manner that the valve member is opened to supply said engine with the fuel while the electromagnetic coil is energized in response to the pulse signal.
It is known in this field of art that the electromagnetic coil requires a large amount of electric energy at the beginning of energization to open the valve member from closed position, whereas it requires a small amount of electric energy after the valve member has been fully opened.
For the purpose of decreasing the electric energy consumption without deteriorating response in valve opening operation, it has been suggested in Japanese Patent 50-7211 published on Mar. 24, 1975 (U.S. Patent application 130,349 filed on Apr. 1, 1971) that the electromagnetic valve is subjected to a constant voltage control and then to a constant current control. Changing the constant voltage control to the constant current control is effected when the electric current flowing to the electromagnetic coil exceeds a predetermined value. Although this control mode is advantageous in that the electric energy consumption is decreased to a minimum and necessary amount, the suggested sequential controls cannot be effected when the voltage across a battery becomes excessively low. When the voltage across the battery which supplies the electromagnetic coil with the electric energy becomes excessively low, the electric current flowing to the electromagnetic coil does not exceeds the predetermined value.